1. Field of the Invention
The present invention relates to a fluid compressor used in, for example, an air conditioner, and furnished with a passage selector valve for changing the passage of a working fluid.
2. Description of the Related Art
In general, there are air conditioners which can perform both air cooling and heating operations. These air conditioners are provided with in- and outdoor heat exchangers and a passage selector valve which serves to change the passage of a working fluid circulating in the heat exchangers when the operation mode is changed between air cooling and heating.
As a typical or prevailing example of the passage selector valve, there is a four-way selector valve which is illustrated in FIG. 3 of Jpn. Pat. Appln. KOKAI Publication No. 60-124595. This selector valve comprises a cylindrical main body and a slide valve therein capable of reciprocating along the axis of the body. In this selector valve, the passage is changed by moving the slide valve straight in the main body.
A solenoid valve is connected to the four-way selector valve, and the slide valve is driven actuating the solenoid valve.
The air conditioner, comprising the four-way selector valve and the solenoid valve, however, has the following various problems to be solved.
First, the air conditioner of this type requires use of a plurality of pipes for connecting the four-way selector valve and the solenoid valve, and the pipe arrangement is highly complicated, thus entailing a bulky construction.
The solenoid valve takes out a low-pressure gas from the intake side of the fluid compressor, and feeds it into a predetermined region in the main body, whereupon the slide valve is driven taking advantage of the difference in pressure between the low-pressure gas and a high-pressure gas filling the body. Thus, it is necessary to provide pipes for taking out the low-pressure gas and introducing it into the four-way selector valve, which require a wide layout space.
The four-way selector valve and the solenoid valve both require a certain length to permit reciprocation. Therefore, the structure which combines these valves cannot be reduced without limitation in size.
Meanwhile, the low-pressure gas pipes for connecting the four-way selector valve and the solenoid valve are very slender capillary tubes (small-diameter copper tubes), and can be deformed and caused to malfunction by a small impact. Since the capillary tubes of the air conditioner are exposed to the outside, they can be easily deformed in particular.
Secondly, the air conditioner requires high-pressure gas pipes for connecting the discharge side of the fluid compressor and the four-way selector valve. Since these pipes are connected to the discharge side of the compressor, they are liable to transmit pulsation (oscillation) of the discharged high-pressure gas to the selector valve. It is necessary, therefore, to take a measure for vibration damping.
As a measure to solve this problem, there is a conventional system which is illustrated in FIG. 4 of Jpn. Pat. Appln. KOKAI Publication No. 60-124595.
This system is a compressor of a type such that a closed casing, which houses a compressor unit and an electric motor unit, is filled with a high-pressure gas discharged from the compressor unit, the casing containing the four-way selector valve and the solenoid valve therein.
Since the four-way selector valve and the solenoid valve are located in the casing of the fluid compressor which is filled with the high-pressure gas, the high-pressure gas pipes can be omitted, and the capillary tubes connecting these valves can be effectively prevented from being damaged by external force.
However, this arrangement cannot solve the first problem that the four-way selector valve and the solenoid valve are complicated and bulky, and arouses another problem that the incorporation of these valves in the casing increases the size of the fluid compressor itself.
Since the four-way selector valve is designed so that the passage is changed by sliding the slide valve in its body, moreover, the slide valve must be intimately in contact with the valve seat at all times. Accordingly, the gas cannot be leaked from between the slide valve and the valve seat when the operation is suspended, so that the pressures in the gas pipes of the air conditioner cannot be balanced with ease.
If the pressures in the gas pipes of the air conditioner cannot be quickly balanced, then restart of the operation after suspension and change of the operation mode between air cooling and heating cannot be carried out with speed.
In an air conditioner adapted for heating operation, on the other hand, if the outdoor heat exchanger is frosted, its performance will be lowered. Conventionally, in the air conditioner of this type, the outdoor heat exchanger is defrosted by supplying a high-temperature, high-pressure gas from the compressor to this heat exchanger through a bypass pipe. In this case, a selector valve for the bypass pipe is provided in addition to the four-way selector valve.
Using the two selector valves, however, this method entails a complicated pipe arrangement. If the bypass selector valve is located in the casing of the fluid compressor, the compressor is further increased in size. Also, more electric wires are led out from the casing, and require a complicated control circuit therefor.